Antireflective coating layer

ABSTRACT

Antireflective structures according to the present invention comprise a metal silicon nitride composition in a layer that is superposed upon a layer to be patterned that would other wise cause destructive reflectivity during photoresist patterning. The antireflective structure has the ability to absorb light used during photoresist patterning. The antireflective structure also has the ability to scatter unabsorbed light into patterns and intensities that are ineffective to photoresist material exposed to the patterns and intensities. Preferred antireflective structures of the present invention comprise a semiconductor substrate having thereon at least one layer of a silicon-containing metal or silicon-containing metal nitride. The semiconductor substrate will preferably have thereon a feature size with width dimension less than about 0.5 microns, and more preferably less than about 0.25 microns. One preferred material for the inventive antireflective layer includes metal silicon nitride ternary compounds of the general formula M x Si y N z  wherein M is at least one transition metal, x is less than y, and z is in a range from about 0 to about 5y. Preferably, the Si will exceed M by about a factor of two. Addition of N is controlled by the ratio in the sputtering gas such as Ar/N. Tungsten is a preferred transition metal in the fabrication of the inventive antireflective coating. A preferred tungsten silicide target will have a composition of silicon between 1 and 4 in stoichiometric ratio to tungsten. Composite antireflective layers made of metal silicide binary compounds or metal silicon nitride ternary compounds may be fashioned according to the present invention depending upon a specific application.

[0001] This is a divisional application of U.S. patent application Ser.No. 09/476,558, filed on Jan. 3, 2000, which is a divisional applicationof U.S. patent application Ser. No. 08/918,690, filed on Aug. 21, 1997,now abandoned, both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. The Field of the Invention

[0003] The present invention relates to the fabrication of integratedcircuits. More particularly, the present invention relates to ananti-reflective enhancement for integrated circuit fabrication. Inparticular, the present invention relates to an anti-reflectiveenhancement for reducing critical dimension loss during mask patterning.More particularly, the present invention relates to formation of a metalsilicon nitride antireflective coating layer that resist “footpoisoning” of a masking layer and its detrimental effects.

[0004] 2. The Relevant Technology

[0005] In the microelectronics industry, a substrate refers to one ormore semiconductor layers or structures which includes active oroperable portions of semiconductor devices. In the context of thisdocument, the term “semiconductive substrate” is defined to mean anyconstruction comprising semiconductive material, including but notlimited to bulk semiconductive material such as a semiconductive wafer,either alone or in assemblies comprising other materials thereon, andsemiconductive material layers, either alone or in assemblies comprisingother materials. The term substrate refers to any supporting structureincluding but not limited to the semiconductive substrates describedabove.

[0006] In the microelectronics industry, the process of miniaturizationentails shrinking the size of individual semiconductor devices andcrowding more semiconductor devices within a given unit area. Withminiaturization, problems arise such as proper electrical isolationbetween components. Attempts to isolate components from each other inthe prior art are constrained by photolithographic limits of about 0.25microns. One way to form structures that electrically isolate conductivematerials on a semiconductor substrate from each other is to usephotolithography in patterning dielectrics layers upon the semiconductorsubstrate.

[0007] To form a metallization wiring layer on a semiconductor substrateby photolithography, a photoresist mask is used to pattern themetallization wiring layer. The mask has directed therethrough a beam oflight, such as ultraviolet (UV) light and deep UV (DUV) light (˜250 nm),to transfer a pattern through an imaging lens from a photolithographictemplate to a photoresist coating which has been applied to thestructural layer being patterned. The pattern of the photolithographictemplate includes opaque and transparent regions with selected shapesthat match, respectively, openings and intact portions intended to beformed into the photoresist coating. The photolithographic template isconventionally designed by computer assisted drafting and is of a muchlarger size than the semiconductor substrate on which the photoresistcoating is located. Light is directed through the photolithographictemplate and is focused on the photoresist coating in a manner thatreduces the pattern of the photolithographic template to the size of thephotolithographic coating and that develops the portions of thephotoresist coating that are unmasked and are intended to remain. Theundeveloped portions are thereafter removed. Other photolithographictechniques for formation of device features are also possible.

[0008] As dimensions shrink below about 0.25 microns, the prior arttechnique of forming metallization wiring layers becomes more difficultto achieve. Light that is reflected during exposure of a photoresisttends to blur the boundary between two metallization lines and the spacetherebetween. This blurring can cause wider metallization lines thandesigned, which excessive width will either bridge and short out thecircuit or will cause unwanted “cross talk” such that the device isrendered defective.

[0009] In general, the blurred edge of a critically dimensionedphotoresist layer caused by reflected light in photolithographictechniques also result in problems in contact corridors, vias, wiringtrenches, and isolation trenches, where the dimensions are patternedbelow about 0.25 microns. For example, a contact corridor that is toowide will cause notching into a gate stack during a contact corridoretch. Notching causes encroachment into conductive areas of an adjacentgate stack and filling the contact corridor with metallization materialcan cause a short to occur between the contact and the conductiveelements of the adjacent gate stack. A wiring trench that is too widewill cause “cross talk” with the wiring in a neighboring trench so as soto compromise speed and accuracy of the integrated circuit associatedtherewith.

[0010] The resolution with which a pattern can be transferred to thephotoresist coating from the photolithographic template is currentlylimited in commercial applications to widths of about 0.25 microns. Inturn, the dimensions of the openings and intact regions of thephotoresist mask, and consequently the dimensions of the shapedstructures that are formed with the use of the photoresist mask, arecorrespondingly limited. Photolithographic resolution limits are thus abarrier to further miniaturization of integrated circuits. Accordingly,a need exists for an improved method of forming semiconductor devicefeatures that have a size that is reduced from what can be formed withconventional photolithography.

[0011] During photolithography, reflected light that occurs duringexposure of a mask tends to blur the desired image because the reflectedlight escapes beyond exposed regions on the photoresist. The blurringproblem is caused by reflected light affecting areas of the photoresistthat are outside the design pattern.

[0012]FIG. 1 illustrates the problem of blurring caused by reflectedlight that occurs during exposure of a photoresist. A semiconductorstructure 10 may be, for example, a semiconductor substrate 12 that wasdesigned to have a width D, but due to blurring caused by reflectivityof patterning light from structures beneath the photoresist,semiconductor substrate 12 has an actual width A. The variance betweendesign width D and actual width A is illustrated as the distance 2(B/2)or B. By way of example, semiconductor substrate 12 was designed to havea width D of 10 in arbitrary units, but due to blurring caused fromreflectivity, the actual width A is nine in arbitrary units. It can beseen that a ten percent variance between design and actual width hasoccurred.

[0013] As miniaturization technology continues, a blurring variance of Bas illustrated in 8 FIG. 1 will increase relative to an ever-decreasingdesign width D. Thus, as also illustrated in FIG. 1, a miniaturizedsemiconductor substrate 12′ that may have a design width D′ of two andone-half in arbitrary units but with the variance of B, will have theeffect of causing a 40 percent error. A variance of B may leaveinsufficient space upon miniaturized semiconductor substrate 12′ to formdesired contacts or structures. It can be seen from the demonstrationillustrated in FIG. 1 that the need to eliminate or substantially reduceblurring must keep pace with miniaturization.

[0014] Another hindrance to photolithographic limitations areconventional antireflective coating (ARC) schemes. Prior art methods foravoiding reflected light and its photoresist blurring problems includeusing layers such as titanium nitride or organic materials that reducethe reflected light in order to better control resolution of thephotoresist. As the ever-increasing pressure to miniaturize bears uponthe microelectronics industry, the conventional antireflectiveenhancements such as a titanium nitride layer, organic layers, or otherlayers known in the art are proving inadequate at resolutions belowabout 0.25 microns.

[0015] One problem at a dimension below about 0.25 microns is that offouling caused by titanium nitride or organic materials. Fouling isdefined as a tendency for a selected antireflective layer to resiststaying within preferred boundaries. Resistance to staying withinpreferred boundaries tends to cause photolithographic techniques to becompromised.

[0016] When the ARC is a polymer film, it is applied directly to thesemiconductor structure to a thickness of about 0.5 microns andphotoresist is deposited on top of the ARC. The ARC then has thefunction of absorbing most of the radiation used during exposure of thephotoresist that penetrates the photoresist material. Both standing waveeffects and destructive scattering of light due to topographicalfeatures are suppressed with use of the ARC. A disadvantage of a polymerfilm ARC is that the process is increased in complexity and dimensionalcontrol may be lost. A polymer film ARC requires application by spincoating of the ARC material and pre-baking of same before applying thephotoresist material. A problem of removing the ARC exists following anetch. For example, during anisotropic etching, portions of a photoresistare mobilized and form a liner within a recess that is being etched thatfurther assists in achieving the anisotropic etch. Due to theanisotropic etch, however, the photoresist that was mobilized may havemingled with other elements that cause it to resist removal byconventional stripping techniques. This resistance to stripping requiresstripping solutions that have a chemical intensity that maydetrimentally effect the structure that was achieved during theanisotropic etch. As such, use of a substance that is intended to aidanti-reflectivity can result in the benefit thereof being mitigated bythe requirement of a more chemically intensive stripping solutiontreatment.

[0017] Various attempts have been made to form antireflective coatingsin order to further enhance miniaturization. One type of antireflectivecoating that has been developed includes metal nitrides, such astitanium nitride, and metal silicon nitrides. The prior art use of metalsilicon nitrides and metal nitrides was developed for resolution limitsat or above about 1.0 microns. At that resolution limit, there waslittle or no concern about the phenomenon called “foot poisoning” of thephotoresist. Foot poisoning is the phenomenon of diffusion of aconstituent of the antireflective layer out of the antireflective layerand into the photoresist material. Foot poisoning has the problem ofchanging the physical qualities of the photoresist material duringprocessing so as to cause the photoresist material immediately adjacentto the antireflective layer to spread or otherwise change. FIGS. 2-4illustrate the phenomenon of foot poisoning as it develops duringphotoresist processing. In FIG. 2 it can be seen that semiconductorstructure 10 includes semiconductor substrate 12. Upon semiconductorsubstrate 12 there may be an insulation layer 14 such asborophosphosilicate glass (BPSG), or a silicate formed fromtetraethylorthosilicate (TEOS) decomposition, or the like. Uponinsulation layer 14 there is disposed a metallization layer 16 that isto be patterned into a system of superficial metallization lines. Aprior art metal silicide or metal silicon nitride antireflective layer18 is disposed upon metallization layer 16 and a masking layer 20 isdisposed upon antireflective layer 18.

[0018] During processing of masking layer, as seen in FIG. 3, a criticaldimension Dc is formed by exposing masking layer 20 to form a patternedmask 22. During curing of patterned mask 22, nitrogen diffuses fromantireflective layer 18 into patterned mask 22 and causes patterned mask22 to expand at the interface between patterned mask 22 andantireflective layer 18. As seen in FIG. 4, patterned mask 22 has formeda foot-poisoned mask 24 in which the critical dimension Dc has been lostand an actual dimension, DA has resulted. When critical dimensions arein the range of about 0.5 to 1 microns, foot poisoning may not be amajor concern. However, the trend of miniaturization has progressed tothe point at which a resulting DA in lieu of Dc is an undesirablevariance. The need to reduce or eliminate foot poisoning can beappreciated as analogous to the need to reduce or eliminate blurring asillustrated in FIG. 1. In other words, foot poisoning effects must bereduced in a manner that keeps pace with the process of miniaturization.

[0019] Another method of attempting to avoid reflected light is to use ametallic mask. Metallic materials, however, can cause contamination ofthe semiconductor structure beneath due to the high mobility of metalions in wet chemical environments or in dry-etch vapors. Additionally,although a metallic mask may remain as part of a finished semiconductorstructure, a metallic mask may not be able to properly withstand highprocessing temperatures sometimes required to achieve a preferredsemiconductor structure.

[0020] What is needed is an antireflective coating scheme that does notsubstantially add to fabrication cost and does not substantially reducefabrication yield. What is also needed is an antireflective coatingscheme that imparts an antireflective quality to photolithographictechniques not previously achieved in the prior art. What is also neededis an antireflective coating scheme that does not cause fouling of thesemiconductor structure. Additionally, what is needed is anantireflective coating scheme that either does not require removal, orthat can be removed without causing contamination or damage to thesemiconductor structure. What is also needed is an antireflectivecoating scheme that facilitates a better photoresist profile and bettercontrol of critical dimensions due to better prevention of reflectedlight than is found in the prior art. What is also needed is anantireflective coating scheme that, while resisting reflecting light,resists foot poisoning of the photoresist during processing.

SUMMARY OF THE INVENTION

[0021] Antireflective structures according to the present inventioncomprise a metal silicon nitride composition in a layer that issuperposed upon a layer to be patterned that would other wise causedestructive reflectivity during photoresist patterning. Theantireflective structure has the ability to absorb light used duringphotoresist patterning. The antireflective structure also has theability to scatter unabsorbed light into patterns and intensities thatare substantially ineffective to photoresist material exposed to thepatterns and intensities.

[0022] Preferred antireflective structures of the present inventioncomprise a semiconductor substrate having thereon at least one layer ofa silicon-containing metallic or silicon-containing metal nitride. Theantireflective layer either absorbs reflected light or dissipatesreflected light into patterns and intensities that do not substantiallyalter photoresist material that is exposed to the patterns andintensities. The semiconductor substrate will preferably have thereon afeature size with width dimension less than about 0.5 microns, and morepreferably less than about 0.25 microns.

[0023] An antireflective structure according to the present inventioncomprises an antireflective layer that resists fouling of thesemiconductor structure such as photoresist foot poisoning and that hasthe ability to absorb light or to scatter light into patterns andintensities that do not substantially effect photoresist material thatis exposed by those patterns and intensities.

[0024] One preferred material for the inventive antireflective layerincludes metal silicon nitrides. The metal silicon nitrides are of thegeneral formula M_(x)S_(y)N_(z) wherein M is at least one transitionmetal, x is less than y, and z is in a range from about 0 to about 5y.Preferably, the Si will exceed M by about a factor of two. Addition of Nis controlled by the ratio in the sputtering gas used in physical vapordeposition (PVD) to deposit the metal silicon nitride material, such asAr/N.

[0025] Minimum reflectivity may be manipulated by adjusting thethickness of the antireflective layer. Minimum reflectivity may also bemanipulated by nitrogen content in the inventive antireflective layer.

[0026] Tungsten is a preferred transition metal in the fabrication ofthe inventive antireflective coating. A preferred tungsten silicidetarget for the PVD process will have a composition of silicon between 1and 4 in stoichiometric ratio to tungsten.

[0027] The inventive antireflective layer is amorphous or has apreferable grain size that is less than the film thickness of theantireflective layer. A grain size that is substantially the same orlarger than the film thickness of the inventive antireflective layerwill cause a substantially discontinuous film to form. A substantiallydiscontinuous film will detrimentally allow for reflected light toescape from the metallization layer that is to be patterned.

[0028] Composite antireflective layers made of metal silicides or metalsilicon nitrides may be fashioned according to the present inventiondepending upon a specific application.

[0029] Another type of composite antireflective layer may be madeaccording to present invention in which antireflective layers made ofmetal silicides or metal silicon nitrides may be combined with rough orhemispherical grained polysilicon. In this embodiment, it may beadvantageous to use the polysilicon as a later-used conductive layersuch as the conductive material in a word line or as an etch stopstructure.

[0030] The reflectivity exhibited by antireflective structures of thepresent invention can be described as the fraction of incident lightenergy that escapes from the surface of the antireflective structurewhen irradiated by photoresist patterning light under normal operatingconditions.

[0031] In connection with preferred materials and preferredreflectivities of selected structures, it is also useful to describe thepresent invention in terms of a variance from the design geometry of anactual characteristic geometry of the structure being fabricated. It canbe appreciated that, as integrated circuit device geometries continue toshrink, the variance preferably either remains relatively constant ormust also shrink.

[0032] The method of the present invention may be used to form variousstructures such as metallization layers. It is to be understood that thediscussion of metallization layers is merely illustrative and notlimiting of the inventive method. For example, isolation trenches,contact corridors, vias, stacked storage node wells, and wiring trenchesare further non-limiting examples of structures that may also be formedby the inventive method and by use of the inventive antireflectivestructure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to illustrate the manner in which the above-recited andother advantages of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof which are illustrated in theappended drawings. Understanding that these drawings depict only typicalembodiments of the invention and are not therefore to be consideredlimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

[0034]FIG. 1 is an elevational cross-section view of a semiconductorstructure, illustrating the variance between a design dimension and anachieved dimension caused by the blurring effect of reflected light inthe distortion of sub-micron critical dimensions in conventionalphotolithography.

[0035]FIG. 2 is an elevation cross-section view of a semiconductorstructure wherein an insulation layer is disposed upon a semiconductorsubstrate, a layer of metallization is disposed upon the insulationlayer, an antireflective layer is disposed upon the layer ofmetallization, and a masking layer is disposed upon the antireflectivelayer.

[0036]FIG. 3 is an elevation cross-section view of the semiconductorstructure depicted in FIG. 2, wherein the masking layer has beenpatterned to form a patterned mask with an ideal patterned criticaldimension.

[0037]FIG. 4 is an elevation cross-section view of the semiconductorstructure in FIG. 2, wherein the masking layer has been patterned toform a patterned mask, and wherein the phenomenon of foot poisoning isillustrated such that a critical dimension has been altered.

[0038]FIG. 5 is a graph of the fraction of total reflectivity as afunction of wavelength for a metal silicon nitride antireflective layerof a given chemical makeup for a series of varying thicknesses.

[0039]FIG. 6 is a graph of the fraction of total reflectivity as afunction of wavelength that illustrates the effect of measuredreflectivity for antireflective layers that differ in nitrogenprocessing conditions during formation of the antireflective layer.

DETAILED DESCRIPTION OF THE INVENTION

[0040] Preferred antireflective structures of the present inventioncomprise a semiconductor substrate having thereon at least one layer ofa silicon-containing metallic or silicon-containing metal nitridematerial. The antireflective layer either absorbs reflected light ordissipates reflected light into patterns and intensities that do notsubstantially alter photoresist material that is exposed to the patternsand intensities. The semiconductor substrate will preferably havethereon a feature size having a width dimension less than about 0.5microns, and more preferably less than about 0.25 microns.

[0041] Materials

[0042] An antireflective structure according to the present inventioncomprises an antireflective layer that resists fouling of thesemiconductor structure such as photoresist foot poisoning, and has theability to absorb light or to scatter light into patterns andintensities that do not substantially affect photoresist material thatis exposed by those patterns and intensities.

[0043] Preferred material for the inventive antireflective layerincludes metal silicon nitrides. The metal silicon nitrides are of thegeneral formula M_(x)Si_(y)N_(z) wherein M is at least one transitionmetal, x is less than y, and z is in a range from about 0 to about 5y.Preferably, the Si will exceed M by about a factor of two. Particularpreferred embodiments include y=2, y=2.55, and z=2.7. For transitionmetals, the at least one transition metal is preferably a refractorymetal such as Sc, Ti, Zr, Nb, Ta, Mo, W, Co, or Ni. Additionally, thetransition metal M may include a combination such as Ti_(r)W_(1-r),W_(r)A_(1-r), or Ti_(r)Al_(1-r) wherein r is in the range from 0 toabout 1. The N in the preferred metal silicon nitrides is added to theantireflective layer during sputtering of, for example a tungstensilicide target or a pair of targets, one of tungsten and one ofsilicon. Addition of N is controlled by the ratio in the sputtering gassuch as Ar/N2. Examples of Ar/N2 flow ratios used in the inventivemethod include Ar/N₂ 30/10, 30/20, 30/30, 30/40, and 30/50. Flow ratesare in standard cubic centimeters per minute (sccm). Thus, 30/20represents 30 sccm Ar and 20 sccm N₂.

[0044] As it has been found that the presence of Si aids in resisting N₂diffusion from the antireflective layer into the photoresist, arelationship is maintained that generally relates an increase of N₂ inthe sputtering gas to an increase in Si in the net sputtering target.Thus, under similar sputtering conditions, the amount of N produced inan antireflective layer according to the present invention in a WSi₂ ora WSi_(2.35) target will preferably be less than the amount of Nproduced in an antireflective layer in a WSi_(2.7) target.

[0045]FIG. 5 is an illustration of measured reflectivity of totalincident light as a function of light wavelength. In FIG. 5, fiveantireflective layers are depicted according to their specific measuredreflectivities. The five antireflective layers have similar chemicalcompositions but have varying thicknesses. The curves in FIG. 5 arelabeled with reference numerals 85 through 200. Each reference numeralcorresponds to a thickness of the inventive antireflective layer inAngstrom units (A). The inventive antireflective layer was made bysputtering a titanium silicide target comprising a TiSi_(2.55)composition. Sputtering was carried out under the conditions of onekilowatt sputtering power, 400-700 volts sputtering potential, and a30/20 Ar/N₂ sccm flow rate and ratio. The 200 Å thick antireflectivelayer was sputtered at 1 kW for ten seconds; the 160 Å thickantireflective layer was sputtered at 1 kW for eight seconds; the 120 Åthick antireflective layer was sputtered at 1 kW for six seconds; the100 Å thick antireflective layer was sputtered at 1 kW for five seconds;and the 85 Å thick antireflective layer was sputtered at 0.8 kW and fiveseconds.

[0046] A simple linear regression of the observed approximate minimumreflectivities of the antireflective layers illustrated in FIG. 5demonstrates a substantially linear relationship between thickness ofthe inventive antireflective layer and minimum reflectivity. The 85 Åfilm has the minimum reflectivity right at the DUV wavelength (˜250 nm).

[0047] Minimum reflectivity may also be manipulated by nitrogen contentin the inventive antireflective layer. FIG. 6 illustrates measuredreflectivity of two inventive antireflective layers, each having athickness of about 120 Å, but having differing concentrations ofnitrogen therein. Each antireflective layer was fabricated under theconditions of 1 kW sputtering power, six seconds sputtering time, and aWSi_(2.55) tungsten silicide sputtering target. The sputteringconditions variable was the nitrogen content in the sputtering gas asillustrated by curves 30/30 and 30/20. It can be seen that sputteringwith a higher nitrogen ratio in the sputtering gas for a 120 Å thickantireflective layer fabricated will have a lower minimum reflectivitythan sputtering with a 30/20 Ar/N₂ ratio. It also has a lower wavelengthtowards DUV at this minimum reflectivity.

[0048] Tungsten is a preferred transition metal in the fabrication ofthe inventive antireflective coating. Tungsten is preferred because ofits ability to form fine (i.e. less than 5 nm) grains of tungstensilicon nitride. Tungsten is also preferred because at a grain size of 5nm or smaller, tungsten grains are substantially amorphous.

[0049] A preferred tungsten silicide target will have a composition ofsilicon between 1 and 4 in stoichiometric ratio to tungsten. A morepreferred tungsten silicide target will have a composition of siliconbetween 2 and 4 in stoichiometric ratio to tungsten. Another preferredtarget will have a silicon to tungsten ratio between 3 and 4.Commercially available tungsten silicide targets may be used andsputtered at different voltage potentials in order to achieve apreferred sputtering ratio of tungsten to silicon. For example, a lowenergy sputtering, e.g. a sputtering at a potential between 400 and 700volts at 1 kW, will tend to have a less preferential sputtering betweenthe tungsten and silicon components in the target. At higher energysputterings, preferential sputtering for tungsten over silicon mayoccur.

[0050] The inventive antireflective layer has a preferable grain sizethat is less than the film thickness of the antireflective layer. Agrain size that is substantially the same or larger than the filmthickness of the inventive antireflective layer will cause asubstantially discontinuous film to form. A substantially discontinuousfilm will allow for reflected light to escape from, for example, themetallization layer 16 that is to be patterned.

[0051] It can now be appreciated that a grain size that is substantially5 nm or less and/or substantially amorphous such as including tungsten,fabricated under the conditions set forth in the specification, can befound using other refractory or transition metals by reading thespecification and by routine experimentation.

[0052] Structures

[0053] Composite antireflective layers made of metal suicides or metalsilicon nitrides may be fashioned according to the present inventiondepending upon a specific application. In many applications, it ispresupposed that a metallization layer such as metallization layer 16 isbeing overlayed with the inventive antireflective layer.

[0054] Another type of composite antireflective layer may be madeaccording to present invention in which antireflective layers made ofmetal silicides or metal silicon nitrides may be combined with rough orhemispherical grained polysilicon. In this embodiment, it may beadvantageous to use polysilicon as a later-used conductive layer such asthe conductive material in a word line or as an etch stop structure.

[0055] Reflectivity

[0056] The reflectivity exhibited by antireflective structures of thepresent invention can be described as the fraction of incident lightenergy that escapes from the surface of the antireflective structurewhen irradiated by photoresist patterning light under normal operatingconditions. Various ways of describing reflectivity may be expressed.For example, a simple fraction of incident light energy may be given fora preferred reflectivity as illustrated in FIGS. 5 and 6. A preferredreflectivity for the present invention is in a range from about 0 toabout 30 percent, more preferably from about 5 to about 20 percent, andmost preferably from about 10 to about 15 percent.

[0057]FIG. 5 illustrates the reflectivity of metal silicon nitrideantireflective layers as a function of incident light wavelength.Standard conditions for the antireflective layers include fabricationthereof from a WSi_(2.55) target with a sputtering gas flow ratio ofAr/N of 30/20. In each case, sputtering was carried out under 1 kW powerconditions, and sputtering times were varied in order to achieve aselected range of thicknesses. It can be seen from the reflectivitycurves in FIG. 5 that minimal reflectivity for antireflective layersmade of metal silicon nitride material is a function of layer thicknessfor the layer thickness tested. Linear regression of approximate minimalreflectivity as a function of layer thickness reveals a substantiallylinear relationship therebetween. It can also be seen that the minimalreflectivity of the inventive metal silicon nitride antireflectivelayers is in the DUV wavelength range of below about 400 nm.

[0058] A second set of antireflective layers was made to discover theeffect of nitrogen content therein upon reflectivity. FIG. 6 illustratestwo antireflective layers of metal silicon nitrides that were made froma WSi_(2.55) target with sputtering gas flow ratios of Ar/N of 30/20 and30/30. As it can be observed, the antireflective layer that wassputtered from a WSi_(2.55) target with a sputtering gas flow ratio ofAr/N of 30/20 has a lower overall reflectivity than the antireflectivelayer that was sputtered from a WSi_(2.55) target with a sputtering gasflow ratio of Ar/N 30/30. The same trend can also be used withincreasing silicon content in a tungsten silicide target.

[0059] By understanding the relationships illustrated in FIGS. 5 and 6,materials may be selected by using such relationships as, for example,the Beer-Lambert law:

I=I ₀exp−(εηd)  (1),

[0060] where I is the reflected light intensity, 10 is the initial lightintensity, ε is the black-body degree of opacity or light extinctioncoefficient of the material, ρ is the density of the material, and d isthe measured distance from the surface of the antireflective structureto a detector.

[0061] It can be appreciated that various metal silicon nitridecombinations can be selected and tested that can be compared with theantireflective layers taught herein. It can be further appreciated thatone of ordinary skill in the art will be able to select fromfouling-resistant, light-dissipating, and light-absorbing combinations,and that a relationship between ρ and ε can be used to choose equivalentmaterials to those that are disclosed herein.

[0062] Blurring Effects

[0063] In connection with preferred materials and preferredreflectivities of selected structures, it is also useful to describe thepresent invention in terms of a variance from the design geometry of anactual characteristic geometry of the structure being fabricated. A maskmay be designed with a first preferred characteristic geometry and, asillustrated in FIG. 1, the actual geometry exposed in photolithographywill vary from the design geometry. With geometries contemplated by thepresent invention, a variance of less than 10 percent is preferred and avariation of less than 5 percent is most preferred. It can beappreciated that, as integrated circuit device geometries continue toshrink, the variance preferably either remains relatively constant ormust also shrink.

[0064] Applications

[0065] The method of the present invention may be used to form variousstructures with preferred geometries such as metallization layers. It isto be understood that the discussion of metallization layers is merelyillustrative and not limiting of the inventive method. For example,isolation trenches, contact corridors, vias, stacked storage node wells,and wiring trenches are further non-limiting examples of structures thatmay also be formed by the inventive method and by use of the inventiveantireflective structure.

[0066] Preferred geometries of the present invention are geometriesbelow 0.25 microns. More preferred geometries achieved by using theinventive antireflective layer are geometries below about 0.22 microns.Even more preferred geometries are below 0.2 microns. Highly preferredgeometries are achieved below 0.1 microns, and the present invention maybe used to achieve patterning geometries of about 0.07 microns.

[0067] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims and their combination inwhole or in part rather than by the foregoing description. All changesthat come within the meaning and range of equivalency of the claims areto be embraced within their scope.

What is claimed is:
 1. An antireflective coating comprising: a materialsubstantially composed of M_(x)Si_(y)N_(z), wherein: M is at least onetransition metal; y is greater than x; and z is in a range from about 0to about 5y.
 2. The antireflective coating of claim 1, wherein Mincludes at least two transition metals of the configurationM1_(r)M2_(1-r), wherein r is in a range from 0 to
 1. 3. Theantireflective coating of claim 2, wherein M1 is tungsten and r is
 1. 4.The antireflective coating of claim 2, wherein M1 is tungsten, M2 istitanium, and r is about 0.5.
 5. The antireflective coating of claim 1,wherein M is tungsten, x is 1, and y is in a range from about 1.5 toabout
 5. 6. The antireflective coating of claim 1, wherein saidantireflective coating has a thickness range from about 25 Angstroms toabout 1,000 Angstroms.
 7. The antireflective coating of claim 1, whereinsaid antireflective coating has a thickness range from about 50Angstroms to about 400 Angstroms.
 8. The antireflective coating of claim1, wherein said antireflective coating has a thickness range from about85 Angstroms to about 200 Angstroms.
 9. The antireflective coating ofclaim 1, wherein y equals about 2x.
 10. The antireflective coating ofclaim 1, wherein y equals about 2.55x.
 11. The antireflective coating ofclaim 1, wherein y equals about 2.7x.
 12. The antireflective coating ofclaim 1, wherein M includes a combination of M1_(r)M2_(1-r), wherein ris in the range from 0 to 1, and wherein M1 and M2 are selected from thegroup consisting of Sc, Ti, Zr, Nb, Ta, Mo, W, Co, and Ni, and whereinM1 is not M2.
 13. The antireflective coating of claim 1, wherein z is ina range from about 1y to about 2y.
 14. The antireflective coating ofclaim 1, further comprising hemispherical grained polysilicon.
 15. Theantireflective coating of claim 1, wherein the material substantiallycomposed of M_(x)Si_(y)N_(z) is a metal silicon nitride ternarycompound.
 16. An antireflective coating comprising: a metal siliconnitride ternary compound comprising at least one metal selected from thegroup consisting of Sc, Ti, Zr, Nb, Ta, Mo, W, Co, Al, and Ni; whereinthe antireflective coating is configured to minimize reflectivity ofdeep ultraviolet light.
 17. The antireflective coating of claim 16,wherein the metal silicon nitride ternary compound is selected from thegroup consisting of titanium tungsten silicon nitride, tungsten aluminumsilicon nitride, and titanium aluminum silicon nitride.
 18. Theantireflective coating of claim 16, further comprising hemisphericalgrained polysilicon.
 19. An antireflective coating comprising: a metalsilicide binary compound comprising at least one metal selected from thegroup consisting of Sc, Ti, Zr, Nb, Ta, Mo, W, Co, Al, and Ni; whereinthe antireflective coating is configured to minimize reflectivity ofdeep ultraviolet light.
 20. The antireflective coating of claim 19,wherein: the metal silicide binary compound is M1_(r)M_(1-r)Si_(s); M1and M2 are both metal and are selected from said group; M1 is not M2; ris in a range from 0 to 1; and s is greater than zero.